Presentation Authors: Yi Quan Tan, Wy Keat Tay*, Li Yin Ooi, Zui Chih Rachel Teo, Ho Yee Tiong, Singapore, Singapore
Introduction: Tumor enucleation for Renal Cell Carcinoma (RCC) along its Pseudocapsule (PC) remains debatable with regards to oncological safety. Multiphoton Microscopy (MPM) combines Second Harmonic Generation (SHG) and Two Photon Excitation Fluorescence (TPEF) to image extracellular matrix architecture. In this study, MPM was used to characterize PCs at the tumour-parenchymal interface to assess intratumoral variation.
Methods: A commercially available laser-based MPM system (Histoindex, Singapore) was used, having the capability to detect and quantify fine collagen dynamics, unobserved with traditional staining techniques. From an Institutional Review Board-approved tissue repository, 20 tissue blocks were retrieved, cut into 4â€Ž-micron sections, mounted on slides and deparaffinized. The PCs were imaged on 20X objective at selected Regions of Interest (ROIs). Corresponding clinical information from our partial nephrectomy database was retrieved. PC thickness was determined. Collagen was quantified by Collagen Area Ratio (CAR), while qualitative collagen parameters measured were Collagen Fiber Density (CFD) and Collagen Reticulation Index (CRI).
Results: 20 pT1 RCC specimens (11 clear cell, 6 papillary, 3 chromophobe) were imaged. 15 patients were male, and mean age was 60.6 +/- 10.6 years. Mean tumour size was 3.32 +/- 1.47cm. There were 5 low, 13 medium, and 2 high complexity tumours on Nephrometry score. Collagen-rich PCs appeared fluorescent green (see Figure 1). Median thinnest and thickest PC areas were 0.5 (IQR: 0.2-0.7)mm and 1.0 (IQR: 0.5-1.1)mm respectively. Median difference between the thickest and thinnest areas was 0.5 (IQR: 0.3-0.7) mm. Median CAR was lower in the thinnest areas (26.1%) compared to the thickest areas (32.9%). Median CFD was lower in the thinnest areas (17.4%) compared to the thickest areas (50.1%), Median CRI was lower in the thinnest areas (11.1) compared to the thickest areas (12.1). No significant differences in CAR, CFD and CRI were found when comparing clear cell against non-clear cell RCC.
Conclusions: MPM demonstrated that the PC is not a homogenous layer at the tumor-parenchymal interface in terms of quantity and quality of collagen. This may be useful for surgeons to be aware of during tumour enucleation for partial nephrectomy.